Reproductive Strategies for Increasing Fertility in Beef Cattle

Abstract

The present research efforts focused on identifying different strategies to increase reproductive efficiency in beef cattle. Reproductive efficiency of beef females has a direct impact on the profitability of beef cattle operations. Therefore, the use of reproductive technologies coupled with appropriate reproductive management has a tremendous impact on beef cattle production. Three experiments were performed to evaluate the effects of a different estrus synchronization approach, use of heterospermic sex-sorted semen and evaluation of the influence of estrus activity and reproductive tract size and position scores on fertility of beef cows. In experiment one, extended length of progesterone exposure for 12 days with additional PGF injection in the middle of the protocol, increased follicular diameter and decreased circulating concentrations of progesterone at CIDR removal in Brahman cows; however not difference in estrus response, ovulation time and pregnancy rates was observed when compared to the Bos indicus PG 5 – Day + CIDR protocol. In experiment two, increased dosage of sex sorted SuperConventional heterospermic semen did not improve pregnancy rates of cows submitted to TAI, therefore, lower semen dosage could be used for Super Conventional semen production, optimizing the collection process. The restricted use of Super Conventional semen for cows that have activated estrus detection patch at TAI and use of conventional semen for cows that do not express signs of estrus can be used as an alternative management approach to achieve higher conception rates and higher percentage of calves with the desired sex while ensuring that cows failing to express estrus the best chance of becoming pregnant early in the breeding season. In experiment three, pregnancy rate at day 30 following FTAI were directly affected by estrus expression and size and position of the reproductive tract (SPS). Pregnancy rates were greatest in cows with smaller reproductive tracts and expressed estrus by AI. Thus, from a management perspective, it may be beneficial to incorporate both an estrus detection system and assign reproductive tract SPS at breeding to make individual breeding decisions.